Electric pulse generating circuit



April 17,1951

w. H. CROWN EI AL 2,548,953

ELECTRIC PULSE-GENERATING CIRCUIT Filed June 7, 1949 //v Vf/V To A;

arm J Patented Apr. 17, 1951 ELECTRIC PULSE GENERATING CIRCUIT William Henry Crown, Leytonstone, London, and

Harold Raymond Whitfield, Ilford, England, assignors to Henry Hughes & Son Limited, Barkingside, England, a company of Great Britain Application June 7, 1949, Serial No. 97,646 In Great Britain June 18, 1948 2 Claims.

The present invention relates to electric pulsegenerating circuits of the kind adapted to generate from a varying control voltage an output voltage varying at a more rapid rate and bearing a predetermined phase or time relationship to the control voltage. For instance it is particularly adapted to the generation of strobe or calibration pulses in radar systems. Such pulse are narrow voltage pulses generated in a fixed phase or time relationship with other varying voltagesfor instance at the beginning of a rising or falling voltage waveform starting from a constant voltage level. For such purposes it has previously been proposed to use combinations of pulse narrowing circuits (such as ringing and differentiating circuits). combined with limtiers (such as diodes) to remove unwanted pulses, and amplifiers to give pulses of sufiicient amplitude for the required purpose. Such circuits entail the use of several valves.

It is the principal object of the present invention to provide a circuit of the kind set forth in which the number of valves required is considerably reduced.

According to the present invention a circuit for generating short electric output pulses having a predetermined time relationship to the variations of an electric input voltage and of duration small compared with the period of variation of the input voltage comprises a thermionic valve pulsegenerating oscillator adapted, when freely running, to generate pulses whose duration is that of the required output pulses and whose recurrence period is less than that of. the input voltage variations, means for applying a standing bias voltage to the said pulse-generating oscillator to render it normally inoperative, means for applying to said oscillator a first voltage derived from said input voltage to render said oscillator operative at the point in the variation of the input voltage at which the output pulse is required, means for applying to the oscillator a second voltage derived from the said input voltage to reinforce the effect of the said standing bias voltage and render the oscillator inoperative, the amplitude and rates of change of the said first and second voltages being such as to allow the oscillator to generate one pulse but insuflicient to allow it to generate more than one in response to a single variation of the input voltage.

The said pulse-generating oscillator may conveniently comprise a multi-electrode valve havin two grids by which the anode current in the valve can be substantially cut oil, the aforesaid standing bias voltage being applied eifectively between these two grids and the cathode and the first and second voltages being applied to the-two grids respectively, the first in a positive sense to render the oscillator operative and the second in a negative sense to render the'oscillator inoperative.

An embodiment of the invention will now be described with reference to the accompanying drawing which shows a circuit for the generation of pulses at the onset of a positive-going, sharplyrising control voltage. A suitable supply for the operation of the circuit is provided between lines I (positive) and 2 (negative and earth). A pentode valve VI is incorporated in a suitable pulsegenerating circuit, shown in this example as a blocking oscillator circuit. The anode of valve VI tive H. T. line I. valve VI is connected to earth through a resistor iron-cored transformer 3, condenser 4 and resistor 5. A decoupling resistor 6 and condenser l are provided in the anode circuit of valve VI and the screen is connected directly to the posi-- The suppressor grid of the H. Components 3, 4 and 5., are chosen in relation to the characteristic of valve VI (in a manner well-known to those skilled in the art) to ensure that, if the cathode of VI were connected directly to earth, pulses would be generated of the width of the desired output pulses and at a recurrence frequency considerably greater than that of the input control voltage. Resistors l6 and i! apply a positive bias to the cathode of VI while a condenser l8 provides a by-pass between the valve cathode and earth. The bias provided is sufficient to prevent free oscillation of the blocking oscillator.

The input voltage from a terminal 8 is applied through a coupling condenser 9 and across a resistor ill to the grid of a valve V2 which is connected as an amplifier with a load resistor l2 between its anode and the positive supply line I and a load resistor 19 between its cathode and the negative line 2. The suppressor grid of V2 is strapped to its cathode and its screen is supplied through a conventional dropping resistor 20 with by-pass condenser 2 I.

Upon the application of a positive-going control voltage to the grid of the valve V2 there are thus generated a negative-going voltage at the anode and a positive-going voltage at the cathode of this valve. These positive and negative-going output voltages are applied to the control and suppressor grids of the valve VI respectively through the condenser-resistance combinations l5 and 5 and I3 and respectively. The values before a further pulse can be generated, a sufficient negative voltage is developed at the suppressor grid to prevent further oscillation. The output may be taken from any convenientpoint in the blocking oscillator circuit depending upon the sign of output pulse required. In the embodiment shown in the drawing positive output pulses are obtained at a terminal 22 connected to the end of the Winding of transformer 3 that is connected to condenser 4.

voltage, said pulses having a fixed time relation to predetermined recurrent variations of said input voltage, said circuit comprising a pulsegenerating oscillator valve to generate when operative pulses having a first recurrence period less than the recurrence period of said variations, said valve having anv anode, a cathode and at least two grid electrodes for controlling the electron stream between anode and cathode, means to applya standing bias voltage between said cathode and said grid electrodes to render said valve normally inoperative, a second valve hav- It will be clear to those skilled in the art that the invention can be readily adapted to generate s, output :pulses from a negative-going input pulse '(by interchanging the connections to the control 1 and-suppressor grids :of the valve V! at the anode and-cathode of the valve V2) and to generate pulsesiat the instants of occurrence of any desired i point in the waveform of a positive or negativegoing voltage :by generating from this voltage, by 'any ofthe well-known methods, a rapidly- ,changing control voltage which is initiated at the desir d. point in the waveform of the firstqnazned voltage :and is suitable for application ;as; an input voltage to the input terminal 8 of yljhg circuitrdescribed. v *Whi-letheinvention hasbeen described with reierence-toa bl cki g. o ci or t w b un g'stood'that any-other suitable pulsegenerator can --h as erts cha am ltivibrator: p

Weclairn: e "1;" A1circuit for generating electric. output pulses of short" duration from an electric input ing an-anodea cathode and at least one control electrode, means for applying said input voltage between the last-named cathode and control electrode,,loadmirnpedance elements connected to the.anodeand'cathode respectively of said second valve and circuit means connecting the anode and cathode of said second valve respectively to said grid electrodes to apply to the last- :named ;electrodesivoltages, of which one serves torender saidoscillator valve operativeiatafirst instant and the other serves to render said oscillator valve inoperative at a second instant, the time betweensaid first and second instants being less than saidjfirst recurrence period.

2. A circuit according to claim 1, wherein each said circuit means comprises a series capacitor and a shunt resistor.

WILLIAM HENRY CROWN. HAROLDRAYMOND WHITFIELD.

. REFERENCES CITED 4 The .following references are of record in the -file ofthis patent: 1 r 1 .li b fName 5 2,193,850 Andrieu et al. F,; Mar; 719 ,1940

2,470,027 Goldberg V May 10, 71949 

